French scientists released a study Wednesday that suggests rats who ate Monsanto’s genetically modified corn or were exposed to its top-selling Roundup weed killer suffered tumors and organ damage.

But Monsanto officials said that similar claims made by the author were "systematically refuted by peer-reviewed scientific papers as well as by the European Food Safety Authority." Monsanto also said that more than 100 feeding studies have confirmed the safety of their biotech crops, and some scientists are questioning the study’s methodology, Reuters reports.

Biologists and neurologists from the University of Caen reported in the study that rats fed a diet with NK603, a seed variety made tolerant to Roundup, or rats that drank water with Roundup at levels permitted in the United States, died earlier than the control group, according to the study, which was published in the journal Food and Chemical Toxicology. It also reported that the animals who ate the genetically modified seeds had mammary tumors and severe liver and kidney damage.

But scientists who have reviewed the study said it did not provide data on how much the rats were given to eat, or what their growth rates were, and that the type of rats used in the study are susceptible to mammary tumors when food intake is not restricted.

Forbes criticized the study, quoting scientists who questioned its methods, particularly that the full data set has not been made available and that the control group was too small.

NewScientist also criticized the study, saying that the researchers did not share their tests to show that the results were statistically significant. Tom Sanders, head of nutritional research at King’s College London, called their analysis a “statistical fishing trip.”

The BBC reported that the researchers refused to provide copies of the journal paper to journalists in advance of its publication, unless they signed non-disclosure agreements, so reporters were not able to have independent scientists review the article.

"Numerous peer-reviewed scientific studies performed on biotech crops to date, including more than a hundred feeding studies, have continuously confirmed their safety, as reflected in the respective safety assessments by regulatory authorities around the world," a Monsanto spokesman said in a statement.

Creve Coeur-based Monsanto Co. (NYSE: MON), led by Chairman, President and CEO Hugh Grant, reported a third-quarter profit of $966 million on revenue of $4.2 billion.